1. Field of the Invention
The present invention relates to a golf club shaft.
2. Description of the Related Art
As a golf club shaft, so-called steel and carbon shafts have been known. The carbon shaft is constituted by CFRP (carbon fiber reinforced plastic).
Most of the carbon shafts are manufactured by a so-called sheet winding process. In the sheet winding process, a prepreg sheet including a fiber and a matrix resin is used. In the process, a sheet formed of prepreg is wound around a metallic core member and the matrix resin is then cured by heating, and the core member is pulled out after the curing. By the process, there is formed a shaft which is obtained by winding and curing the prepreg sheet.
Japanese Laid-Open Patent Publication No. 2003-24489 has disclosed a carbon shaft in which a straight layer, an angle layer and a hoop layer are provided and a tensile modulus of elasticity of a fiber or the like is specified. Referring to the shaft, it is possible to achieve a lightweight property and a high strength. US Patent Application No. US2003/022728 A1 corresponds to the Japanese Laid-Open Patent Publication No. 2003-24489.